1. Field of the Invention
The present invention relates to a method for allocating addresses to a Network Interface Card (NIC) included in a host that uses a Transmission Control Protocol (TCP)/Internet Protocol (IP) in a Local Area Network (LAN) environment, and more particularly, to an apparatus and a method for allocating a plurality of IP addresses to one NIC. The present application is based on Korean Patent Application No. 2001-54457, filed Sep. 5, 2001, which is incorporated herein by reference.
2. Description of the Related Art
A Network Interface Card (NIC) is necessary to access an Ethernet. The NIC accesses an Ethernet using a unique Media Access Control (MAC) address allocated in a manufacturing stage while a host has its own Internet Protocol (IP) address corresponding to a hostname.
The MAC address is a physical identity (hardware address) necessary to identify a computer or equipment connected in a Local Area Network (LAN) and is used as an Ethernet address in the Ethernet LAN. An IP address (logical address) is used to transmit packet data over the Internet. However, if the data arrives at a destination LAN, the IP address should be converted into the MAC address so that a destination host can receive the data.
The MAC address is used in a MAC layer, which is a sublayer of a Data Link Control (DLC) layer in a communication protocol.
If a user has a computer running Windows (Windows is a trademark of Microsoft.), he can identify the IP address and the MAC address by entering “winipcfg” after selecting a Start menu and an Execution menu.
When the TCP/IP protocol is used to access the Ethernet, the IP address needs to be converted into the MAC address. Then, actual IP addresses and actual MAC addresses are mapped to each other.
Therefore, if the number of IP addresses necessary for the host is N, the number of required NICs is also N.
FIG. 1 is a block diagram showing the configuration of an apparatus that accesses the Ethernet in a conventional address allocation method. In FIG. 1, the upper part of the thick solid line shows subsystems in a host while the lower part shows subsystems included in an opposite host.
A File Transfer Protocol (FTP) processor 102 converts a hostname into an IP address of 32 bits using a Domain Name System (DNS) and then, attempts to access a Transmission Control Protocol (TCP) processor 104 using the given IP address. The TCP processor 104 converts the connection request segment into an IP datagram for transmission to an IP processor 106.
If the opposite host is in a local network in an IP layer, the IP datagram is transmitted to the opposite host through the local network directly. If the opposite host is in a remote network, the IP datagram is transmitted to the next router by means of the IP routing function.
The IP datagram refers to a unit of data transmitted or received in the IP layer and corresponds to the packet in the Ethernet.
Since the Ethernet uses an address of 48 bits, an IP address of 32 bits should be converted into an address of 48 bits by an Address Resolution Protocol (ARP).
An ARP processor 108 converts the IP address of 32 bits into the Ethernet address of 48 bits, and vice versa. If the host 100 transmits data to the opposite host, the ARP processor 108 broadcasts the Arp Request Frame to all the hosts.
The ARP processor 118 of the opposite host receives the Arp Request Frame transmitted by the ARP processor 108 and, as a response, transmits the Arp Reply Frame including its own hardware address (Ethernet address) to the ARP processor 108.
If the ARP processor 108 receives the Arp Reply Frame transmitted by the ARP processor 118 of the opposite host, it prepares for transmitting the IP datagram. Then, the IP datagram is transmitted to the opposite host.
The Ethernet driver 110 corresponds to an NIC and transmits data in a physical layer.
Each NIC has its own Ethernet address of 48 bits while a host has one IP address of 32 bits. Actual IP addresses and actual MAC addresses are mapped to each other.
As a result, the existing address allocation method is not cost-effective in that the N IP addresses required in a host necessitate the same number of NICs.